I'm saying this because I recently watched a scene where a man gives another man his helmet because his cracked, they had trouble breathing the atmosphere and from my own research it seems they both would have likely gotten high. From what I can tell the oxygen level of the planet is maybe around 10 to 15 percent? given that they didn't imminently lose consciousness which has been reported (from a document i looked up) to happen in these conditions when the oxygen level is 10 percent or lower.


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    $\begingroup$ we live in a primarily nitrogen atmosphere... $\endgroup$ – Alex Robinson Apr 3 '17 at 14:52
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    $\begingroup$ Could you please link this "document I looked up" it might provide some clarity $\endgroup$ – Cameron Leary Apr 3 '17 at 14:52
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    $\begingroup$ this question is more suited for medical forum, not for world building $\endgroup$ – L.Dutch Apr 3 '17 at 15:13
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    $\begingroup$ If you can be more specific about the composition of the atmosphere you're talking about (how much oxygen/nitrogen/argon), and provide more detail about the specific question you're asking here (could they survive, how long would they survive, would they get high, would they lose consciousness), then this might be more answerable. $\endgroup$ – DaaaahWhoosh Apr 3 '17 at 18:07
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    $\begingroup$ Just a quibble, but I seem to recall percent is not as important as partial pressure. And you reach the partial pressure of ~10% O2 (sea level) around maybe 15000 feet on earth. $\endgroup$ – user25818 Apr 3 '17 at 18:31

It's entirely an asphyxiation risk, not a toxic issue.

Just for fun...Argon has the opposite effect of Helium...speaking with high amounts of Argon in your lungs produces a much deeper tone than Helium. Expect these people to speak in very low tones, Barry White has nothing on these guys

Other answers touch on it, but full issue is - Argon is heavy. It sinks in the atmosphere and finds lows to gather in. If your characters are on a hill or in a windy environment, this might not be as much of an issue. If they are in a valley, the argon will pool, replacing all oxygen, and cause death. Ugly too, breathing fine, but dying from lack of oxygen anyway.

Argon will also pool in your lungs. Prolonged breathing of it will see Argon start to gather in the lungs and not be easily replaced, once again becoming an asphyxiation risk. Even if there is ample oxygen in the air, the argon prohibits it from getting to the lungs. Causes short rapid breathing before asphyxiation. This is actually why Helium voice is generally ok while Argon voicing is considered highly dangerous.

Remember, the oxygen requirement we have is based in pressure, not simply percents. We require around .2 Atm of oxygen for our respiration. Maybe a different question, but 10% oxygen in double the pressure environment could see us breathing safely. I'd have to research the topic further

  • $\begingroup$ So, if you find yourself in an Argon atmosphere where you have plenty of oxygen, you should stand on your head, right? :-) $\endgroup$ – ShadoCat Apr 4 '17 at 0:44
  • $\begingroup$ Argon has an atomic weight of 40. Carbon dioxide has a molecular weight of 44. CO2 doesn't pool in our lungs enough to matter, why would Ar?? $\endgroup$ – Loren Pechtel Apr 4 '17 at 1:21
  • $\begingroup$ @LorenPechtel It does. Normally, CO2 concentration is at parts-per-million range, so not much of a problem, but if the percentage of CO2 raises it causes the same problems of suffocation than argon would. That's why you can kill yourself with the exhaust gases from a car. $\endgroup$ – Rekesoft Apr 4 '17 at 9:33
  • $\begingroup$ @Rekesoft I thought it was the carbon monoxide in the exhaust that killed you. $\endgroup$ – Michael Vehrs Apr 4 '17 at 14:54
  • $\begingroup$ @MichaelVehrs Sometimes it's carbon monoxyde, sometimes it's carbon dyoxide. If I'm not wrong, carbon monoxyde is produced by a faulty combustion (there's no oxygen enough to fully burn the fuel). It can happen if, say, you have a faulty stove in a closed roorm. But for the scenario of tube-from-exhaust-to-the-window-car I expect carbon dyoxide replacing oxygen would kill you first. I'm not in the mood of testing it out, though. $\endgroup$ – Rekesoft Apr 4 '17 at 15:24

Humans have always lived in a primarily nitrogen atmosphere.

To quote Wikipedia

By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide.

Argon is non-toxic. As long as the oxygen content remains around 20% you can have as much argon in the air as you want.

  • $\begingroup$ so say the argon content is enough to be problematic, how long would a human live for, if they were trading one helmet between each other? $\endgroup$ – Martyn Bell Apr 3 '17 at 14:53
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    $\begingroup$ It's not the argon content that's the problem it's to oxygen percentage. $\endgroup$ – sphennings Apr 3 '17 at 14:54
  • $\begingroup$ okay so if they start choking we can assume its a low amount of oxygen, so (and i know ur just going off ear here with no visual reference or numbers) would it be possible to survive in a situation like this environment with low oxygen by trading a helmet between one another, even if one of them loses consciousness? i know that this type of environment can cause frostbite from what i've read $\endgroup$ – Martyn Bell Apr 3 '17 at 15:06
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    $\begingroup$ Choking is in response to carbon dioxide buildup not lack of oxygen. In situations where an environment has lost it's oxygen due to low pressure or displacement by another gas people will pass out before they notice anything is wrong unless other warning systems are in place. $\endgroup$ – sphennings Apr 3 '17 at 15:11
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    $\begingroup$ This is probably helpful. youtube.com/watch?v=kUfF2MTnqAw Has some numbers to watch and will give you an idea of just how long a human can go and be "fine" in a low-oxygen environment. Swapping a helmet back and forth would likely work, though the one with the helmet would have to closely watch the one without. $\endgroup$ – Draco18s Apr 3 '17 at 15:53

Argon is a noble gas; its chemical reactivity is so low you can effectively treat it as "filler" to keep the pressure up. Likewise, the bonds that make up diatomic nitrogen are so stable that they don't play any role in human respiration. (Certain bacteria can fix nitrogen, but that's out of scope for this discussion.) Those two gases make up 80% of our atmosphere, and other than relative mass they contribute to planetary air pressure, I see no reason why their ratio would be significant in breathing.

One thing we haven't considered, however, is air pressure. As pressure goes up, there is a risk of nitrogen narcosis, where atmospheric nitrogen gets into your blood and affects your brain function. This is why deep-sea divers use helium in their mix. That stack exchange article also mentions that the percentage of oxygen you need goes down as well when operating at a higher pressure; so increasing this pressure would increase risk of narcosis while reducing the need for 20% oxygen in your mix.

Even at "normal" pressures, however, SCUBA diving is probably a good metaphor for the story you describe. In their case, most of the air has been displaced by water, which we also can't breathe. In the old days of SCUBA, divers were trained to buddy breathe, sharing a single regulator between them in case of an equipment failure. This sounds a lot like the fictional story you describe, where the two characters are buddy breathing with a single helmet.

  • $\begingroup$ Buddy breathing via swapping helmets sounds complicated. Especially since you'd need to re-purge the helmet after every swap. $\endgroup$ – sphennings Apr 3 '17 at 17:10

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